The coffee plant is a shrub or small tree about three to three and a half meters tall, and its red or purple fruit is botanically an epigynous berry or indehiscent drupe. The bean is really a seed, neither a true cherry nor a legume. The fruit takes about nine months to ripen, usually holds two flat sided seeds, and in 5 to 10% of cases holds a single round peaberry. An Arabica tree needs three to five years to bear fruit and can produce for 50 to 60 years, sometimes up to 100, which locks farmers into long term bets. Plants of the World Online lists 133 accepted species plus one natural hybrid, yet Arabica and canephora make up nearly all production.

Arabica, from the Ethiopian highlands and Sudan’s Boma Plateau, is itself a cross of canephora and Coffea eugenioides. The coffee genome, sequenced in 2014 with over 25,000 genes, showed that coffee evolved caffeine with different genes than tea or cacao. Caffeine poisons insects that eat the leaves, while small doses in nectar help honeybees remember the flower’s scent. New species keep appearing, including seven from Madagascar named by Kew researchers in 2008 and 2009 and the naturally caffeine free Coffea charrieriana from Cameroon.

• The earliest coffee species had little or no caffeine.
• In 2011, 20 species from the genus Psilanthus were moved into Coffea after DNA evidence, extending its native range into tropical Asia and Australasia.
• The coffee borer beetle and the coffee leaf miner are climbing the mountains along with rising heat.
• A 2020 study showed SSR marker analysis can fingerprint coffee plants and trace green coffee to its genetic source.
• Coffee leaf tea, cascara from the cherry, and soft drinks made with coffee fruit extract use more of the plant.